Electromagnetic/inductive mode (tightly coupled) or resonant mode (loosely coupled) coupling includes the near field wireless transmission of electrical energy between two conductors, such as magnetically coupled coils. The amount of electromagnetic/inductive coupling between the two conductors is measured by their mutual inductance, which in many instances can be determined by the formula M=k*(Ls*Lp)^0.5, where k is the coupling factor, and Ls and Lp are the inductance for a secondary side and a primary side conductor, respectively. The amount of electromagnetic/resonant coupling between two conductors is measured by their figure of Merit “U”, which in many instances can be determined by the formula U=k*(Qs*Qp)^0.5, where k is the coupling factor, and Qs and Qp are the quality factor for a secondary side and a primary side conductor, respectively. More specifically, the figure of Merit “U” is the efficiency of coupling between two coils resonant at the same natural frequency, where the respective quality factor, Q(w)=w*max energy stored/power lost, with w being equal to 2πf, where f is the frequency. In each instance, the power transfer can be increased by increasing the coupling factor, k.
The coupling factor, k, between the two conductors can be increased by winding them into coils and placing them relatively proximate to one another in an orientation in which a magnetic field induced in one of the coils intersects and/or passes through the other one of the two coils. The transmission of electrical energy via electromagnetic/inductive/resonant coupling has been used to exchange information as well as to transfer energy between two objects. Transferring energy via electromagnetic/inductive/resonant coupling is also sometimes referred to as wireless charging, and is a feature that is being increasingly supported in portable electronic devices.
The various technologies associated with wireless charging generally involve the arrangement of the device to be charged with a charging station, such that an electromagnetic/inductive/resonant coupling interaction is created between a coil associated with the device to be charged and a coil associated with the charging station. The electromagnetic/inductive/resonant coupling interaction generally involves an electromagnetic field produced by a current in the coil associated with the charging station which is intended to induce a voltage and/or current in the coil associated with the device to be charged. The induced current is in theory of a sufficient magnitude, such that it can be collected and used to power the device and/or used to recharge a power storage element such as a battery, which can then be later used to power the device. However, the degree and/or efficiency with which power can be supplied through the electromagnetic/inductive/resonant coupling is often dependent upon the proximity, orientation and arrangement of the two sets of coils and/or conductors, which are respectively associated with the charging device and the device to be charged.
The charging device could be expected to interact with multiple different types of devices, where each device might have a different arrangement with its own unique coil configuration including an associated size and shape. In other words, different types of devices may have different sized sets of coils, where for example a lap top or tablet computer might have a relatively larger sized set of coils, while a cellular radio frequency telephone might have a relatively smaller sized set of coils for supporting an electromagnetic/inductive/resonant coupling. An electric automobile, that might support wireless charging might have a still larger set of coils. In at least some instances, a charging device might be expected to separately or simultaneously support the supply of power to each of multiple types of devices. As such, there is a desire to be able to manage, to at least some degree, the ability of the wireless charger to electromagnetically and/or inductively interact with the device to be charged.
The present inventors have recognized that, because the charging device and/or the device to be charged may be expected to interact in multiple different types of charging environments, where the charging device and/or device(s) to be charged may have varying configurations, a charging device and/or a device to be charged that has a coil configuration that can be more readily adjusted and adapted to different types of charging environments may be beneficial.